Fluid-pressure-actuated tool



Filed oct. 16,l 1920 Cil ERNEST H. SHAFF, 0F GRAND HAVEN, MCI-IGAN, ASSIGNOR TO W'ILL'IAM'H; KELLER, INC., 0F GRAND HAVEN, MICHIGAN, A CRPRATION OF MC-IGAN;

rLUIn-rnnssnnn-aoruarnn Toon.

Application filed Getobcl 16, 1920. Serial No. 4173420.

"r vide for a more rapiddecrease in the pressure returning the piston toward the end of the stroke than has heretofore been obtainable, thereby reducing the recoil at the end of the return stroke.

Further objects and advantages of my invention Will become apparent as the description proceeds. Y

In the accompanying drawings Figure l is a sectional vieuT of 'a pneumatic hammer illustrating the application of my invention thereto and Fig. 2 is a similar view on a somewhat enlarged scale showing the valve in the-other position.- Fig. 3 is a fragmentary radial section of the tool through the passage 52 shown in F ig. 2. The genera-l construction and operation of this type of hammer being disclosed in detail in my copending application hereinabove referred to, detailed explanation thereof is deemed unnecessary. n The tool comprises, briefly, `a body vmember l0 defining a cylinder in which the piston 12 reciprocates to strike a suitable Working tool 14; a valvefcasing comprising annular members 16 and 1 8 supporting and guiding the valve 20, and a head 22 threaded onto the body and locked in assembled rposition by a locking clip 24. A throttle valve operated by the lever 26 controls air through passage 28 to an annularchamber 30.

lith the valve in the position shown in Figure l live motive fluid venters through radial passages 32 terminating in the annular groove 34 and forces the piston forward to strike va blow aga-inst the tool. The dead air in front of the piston flows from the front end of the'tool through one or more passages 86 to the annular groove 38 in the valve casing which, as shown in Fig. l, is in communication with the exhaust groove 40 from which exhaust groove, passages 42 opening under 'the clip 2.4 allow the fluid to escape into the atmosphere.

In its forward movement the piston uncovers the small port 44 Which raises the Y sage 42.

' passage 56 immediately rises and the valve pressure inthe passage 45 considerably before'the piston toward the end of its stroke covers the' end of passage 48 and m'icovers the end of jassage 46. VVh/en this occurs, live motive .fluids flows through passage 4G and entersithe large valve chamberl) thereby throwing the valve l ack immediately to the position shown in Fig. 2. The air in chamber Obackfoftheevalve vflange may escape through passage 5l into exhaust pas- During rthis lmovement of the valve live motive fluid iills the` passage 48 which, after passage 46 has been out olf Yfrom the large valve chamberl 50,1continues to yexert pressure on the valve and hold 1t in 'its rearmost position.

The movement of the valve to the position shown 1n F 1g. 2 covers groove 34 and.

uncovers the exhaust `groove 40 so .that live motive fluid is cut off from the rear portion ofthe cylinder and the latter is placed in. direct communication with the atmosphere. The valve in its Y*rearward Ymovement also uncovers the forward end of a passage putting -it int-o communication with -groove 38 and'passage 36. Passage 52 extends radially outward at 54 to receive live motive fluid rfrom 4the annular chamber 30, which tlui-d is deliveredthrough passage 36 tothe front end of the cylinder to return the piston. On account of the rela-tively small size of passage- `52' "the pressure during the return stroke'ivill fall ofi' rather rapidly es- (iii pecially toward the end of the ,stroke when.v

the piston has attained a` fairly high veloc-.'

ity.' KAThen the piston uncovers passage 48, the v`pressure of the fluid in this 'passage Will fall to the same pressure as that in the front end of the cylinder, which pressure as above noted Will decrease considerably during they return stroke.

Toward the end of the return stroke the piston covers the end of the passage 56,-the other end of which communicates with the small valve chamber 58,. A small port '60V continuously communicates With lthis passage and with the annular chamber 30. The

pressure in the passage cannot rise during thereturn stroke because the end of the passage is in communication with the rear end of the cylinder until the piston covers l/Vhen this occurs, the pressure in the is thrown forward again into the position sho-Wn in Fig. l. This takes place against Athe pressure existing at the instant in the large valve chamber which is the same the pressure in the front end of the cylinder by reason of vpassages 48 which are continually in communication with the large valve chamber and the front end of the cylinder. ls soon as the valve has shifted, however, the front end of the cylinder is again connected to theV exhaust passages through passages 36 so that during the for-l ward stroke the pressure in the large valve chamber will be practically atmospherieand i firmly in the position in the position shown in Fig. 2, the supply pressure in the small valve chamber 581 is not sufficient to shift the valve forward. The point at which this limit is reached depends largely on the pressure in the front end of the cylinder, which through passage 48 controls the pressure in the large valve chamber.

According toV my invention l provide a small auxiliary port 62 in passage 46 opening under clip 24 'directly into the atmosphere. 'lliis passage, especially when the supply pressure is low and the volume delivered correspondingly small, will materially out down the pressure in the front end of the cylinder when the piston is far enough back on its return stroke to uncover passage 46 thereby reducing the pressure in the large valve chamber and making it possible to operate the tool at slower speeds than would otherwise be obtainable.

During the operation of the tool under full pressure it also materially diminishes the recoil at the end of the return stroke by cutting down the pressure returning the piston after the piston uncovers the end of passage 46. It is thus possible by slightly increasing the sizeof passage 52 to secure the same speed of operation byaccelerating the piston slightly faster during the first half of the return stroke and slightly less after passage 46 isr uncovered, getting the piston back to the rear end of the cylinder in the same length Vof time, but with a materially lower filial velocity and with less pressure inv front of itat the instant of revers al.

'While I have illustrated and described in detail the preferred embodimentv of my inneoacia ven-tion, it should be clearly understood that the disclosure is merely for purposes of illustration and that many modifications and variations will naturally occur tolthose skilled in the art. l aim in the subjoined claims to cover all such legitimate variations and modifications.

l claim as my invention l. fr pressure-tluid-actuated tool Vom pri. in combination with a cylinder rolled by the piston as it approaches the nd of its forward movement for admitting iressure fluid from the piston chamber to he larger pressure chamber whereby to Ashirt the valve member, l c i and means includg a passage intermittently opened to en` for relieving the pressure in the pressure chamber in the return ment of the piston, and substantially refore it reaches the end of its stroke, the piston near the end of its return stroke serving to close said passage whereby to el'lect the forward shifting vof the valve member. K

A pressure-tluid-actuated tool comprising', in combination with a cylinder iaving a piston, valve mechanism controlling the piston comprising valve meinber, a small pressure chamber and a large pressure chamber, means for admittinga constant supply of live motive fluid to the small pressure chamber, neans including a passage controlled by the piston near the beginning' of its forward movement for substantially relieving the pressure in the smaller cha aber, A'ieans controlled by the aiston as'it approaches the end of its forward movement for admitting pressure fluid from the piston chamber to the largo pressure chamber whereby to shift the valve member, and means including a constantly open exhaust port from said shifting means for relieving the pressure from the cylinder in front of the piston during the latter portion of its return stroke, thepiston also serving nea-r the end of its return stroke to close said' passage whereby to ellect the forward shifting of the valve member.

ln, testimony whereof, l have hereunto set my hand.

.smallerv chamber, means con- Y 

